Dietary patterns in early pregnancy are associated with distinct gut and vaginal microbial profiles: Insights from the MicrobeMom study

Alterations in gut and vaginal microbial communities during pregnancy have been linked to adverse maternal and neonatal outcomes. Diet is a major modifiable factor that can shape the microbiome, through processes such as fibre fermentation and short chain fatty acid production. This study aimed to examine how dietary patterns relate to variation in gut and vaginal microbiome profiles in early pregnancy among healthy participants ( n = 130) from the MicrobeMom trial. At 16-weeks' gestation, diet was assessed using 3-day food diaries to calculate five dietary indices: AHEIP, MD, PHDI, DASH, and DII. Stool and vaginal samples underwent shotgun metagenomic sequencing. In adjusted models, higher DASH scores were associated with lower vaginal Shannon diversity (β = −0.01, p = 0.04). Gut microbiome composition differed between ‘High’ and ‘Low’ AHEIP groups ( p = 0.005, R 2 = 0.02), while vaginal CST distribution also differed between AHEIP groups ( p = 0.03). Unadjusted DASH-gut and DII/AHEIP-vaginal beta diversity associations did not persist after confounding adjustment. In this exploratory analysis of a healthy, predominantly White Irish cohort, maternal dietary quality was associated with modest differences in gut and vaginal microbial patterns in early pregnancy.